In known manner, submerged repeater equipment is mounted in a watertight protective metal case contained in or constituting a cylindrical cask or housing of high mechanical strength, in particular as regards withstanding traction forces. The housing is fixed at each of its ends via a hinge system to a housing of analogous strength containing a line cable splice box for connection to the line cable. Each end of the metal case of the repeater is equipped with a lead-in cable connected to the internal equipment of the repeater via a watertight bushing through the wall of the case. The lead-in cable is referred to as the "repeater access cable". When the installation is being laid, the free end of the access cable is connected to the line cable inside the splice box, and is fixed in the wall of the splice box via a coupling where it enters the splice box.
The repeater access cable is formed of a conductive tube conveying the current for remotely powering the repeater from the splice box, which tube is covered by a polyethylene sheath providing electrical protection therefor, and encloses optical fibers which are thus protected, which lie stress-free inside the tube, and which provide transmission between the splice box and the repeater. The tube is corkscrew-shaped at least on leaving the repeater so as to have a certain amount of flexibility at the hinge system for linking the outer housing of the repeater to the outer housing of the splice box.
At the free end of the access cable, extra length is left on its fibers so that they project beyond the end of the tube, and they are connected to the line cable inside the splice box. Also at the free end of the access cable, the coupling mounted on the tube stripped of its sheath is fixed in the entrance of the splice box. The coupling further receives the remote powering current transmitted via the tube to the repeater. After the access cable has been connected to the splice box, the splice box and the coupling are coated with a sheath made of polyethylene injected under pressure, overlapping onto the sheath of the access cable, and providing overall sealing at the splice box.
This method of connecting a repeater to a line cable is described in particular in French Patent Application FR-A-2 606 943. In that Document, the coupling equipping the end of the access cable is provided such that it constitutes a mechanical fuse which breaks when abnormally strong forces are exerted on the access cable. Such forces occur essentially while the access cable is being handled during connection of the repeater to the line cable, and during injection of the sheath coating the splice box and the coupling together with the adjoining sheathed portion of the access cable. Such forces can cause the fixing between the coupling and the entrance of the box to break in order to avoid damage at the repeater end, which damage may give rise to ingress of water into the case containing the repeater.
This point of weakness at the fixing between the coupling and the entrance of the splice box leads to relatively complex dispositions being provided at the entrance of the splice box with corresponding relatively long times being required for laying the link. Furthermore, when the fixing between the coupling and the entrance of the splice box breaks, the fixing (currently generally performed by soldering) between the coupling and the end of the tube in the access cable also often breaks, at least partially, and needs repairing.
An object of the present invention is to equip the free end of a repeater access cable with a coupling for fixing it to the splice box, the coupling having mechanical strength comparable to that of the access cable itself and making it possible both to simplify the method of fixing to the splice box, and also to reduce the time required for fixing and the overall time required for any repair.